The present invention relates to a micro-motor employed in portable electronic apparatuses or home-use electronic apparatuses such as game machines.
Some of portable electronic apparatuses use a motor. Manufacturers in this trade are fiercely competing with each other in downsizing and reducing weight of their products. Particularly in the market of portable-information apparatuses including cellular phones, the manufacturers have been competing for weight reduction by 0.1 g. On the other hand, a motor to be mounted to a portable apparatus is expected to withstand a strong enough shock produced when the apparatus is dropped. The motor thus must accommodate two contradictory subjects, i.e., downsizing and strengthening.
One of the conventional motors discussed above is disclosed in the Japanese Patent Application Non-Examined Publication No. 2000-50597. FIG. 6 shows this motor. Rotation of the motor, i.e., the rotation of shaft 358, entails vibrator 356 mounted to shaft 358 to spin. Because vibrator 356 shapes in an unbalanced form, the spin produces vibrations. If a cellular phone employs this motor, the vibrations can notify the phone-user of a message arrival.
In FIG. 6, pipe 352xe2x80x94fixing magnet 354xe2x80x94is disposed within socket frame 351. In this structure, when a shock is applied to the motor due to dropping the phone, the loads of vibrator 356, coil 355, magnet 354 and others are applied to pipe 352. Enough strength is thus needed for holding frame 351 and pipe 352 together.
Greater load is applied at a shock when larger vibrator 356 is used for obtaining greater vibrations, and the load exceeds the strength holding frame 351 and pipe 352 together. Then pipe 352 slides off frame 351, and coil 355 touches frame 351, so that the motor fails to spin. As a result, a vibrator size is restricted and the motor should be mounted to an apparatus at a place free from a great shock.
Fit-in margin raging from 20 xcexcm to 30 xcexcm between socket frame 351 and plug pipe 352 is needed in order to maintain sufficient holding-strength therebetween when they are press-fitted. Thus sintered bearing 357, which is press-fitted into pipe 352, receives pressure from the outside, and the inner diameter of bearing 357 is contracted, which produces irregular inner diameters. As a result, bearing 357 fails to keep shaft 358 stably, and unstable r.p.m. of the motor is expected.
The present invention addresses the problems discussed above, and aims to provide a motor, which can withstand a strong enough shock due to a drop and avoid any changes in both characteristics and functions. The present invention also aims to provide an apparatus employing the same motor. Further, when the motor of the present invention is going to employ a vibrator, it can employ a larger vibrator than a conventional one because the motor is equipped with strong enough shock-proof strength. Greater vibrations can be thus obtained, and a vibration micro-motor with a stable r.p.m. and excellent characteristics can be realized. An apparatus employing the same motor can be also provided.
The motor of the present invention comprises the following elements:
(a) a cylindrical frame made of ferromagnetic material;
(b) a pipe fitted-in and disposed within the frame concentrically, where the fitted section between the pipe and the frame is welded;
(c) a sintered bearing press-fitted inside the pipe;
(d) a cylindrical magnet fixed on an outer wall of the pipe at its inner wall; and
(e) a cylindrical coil facing the magnet via an annular space.
An apparatus of the present invention comprises the following elements:
(a) a housing;
(b) a motor disposed in the housing, where the motor has the structure discussed above; and
(c) a power supply mechanism for powering the motor.
This structure allows the holding strength between the frame and the pipe to be greater than the conventional one, which has been produced by press-fit of both the elements. Thus the pipe is prevented from being slid off the frame due to the shock produced by dropping the apparatus, and the problem of changes in the characteristics as well as in the functions can be solved. The apparatus employing this motor can withstand a strong shock corresponding to the improved shock-proof capability of the motor.
Since the fitted section between the frame and the pipe is welded, the pipe can be lightly press-fitted into the frame as a pre-treatment. Therefore, the sintered bearing disposed inside the pipe receives less pressure from the outside, and the bearing is free from variations in its inner diameter, so that the motor can produce a stable r.p.m. with excellent characteristics.
In an apparatus which is going to employ a vibration motor having a vibrator, a vibrator larger than a conventional onexe2x80x94corresponding to the improved shock-proof strength of the motorxe2x80x94can be used, so that the apparatus can obtain greater vibrations. The apparatus thus becomes ideal for notifying an apparatus-user of a message arrival with vibrations.